Digital media is a form of electronic media where data is stored in digital form. Development of technology has facilitated easy copying and transmission of digital media due to which digital media can be easily manipulated, distributed, and rendered (played) by devices, such as video players and computers, and is easily transmitted over computer networks. Due to digital media being pervasive and easily manipulated, illegal activities, such as unauthorized distribution, duplication and modification are becoming more prevalent and are subsequent to digital piracy. Hence, techniques to protect owner's right of the digital media are in demand.
Digital watermarking is used as a means to protect owner's right. Digital watermarking is a technique of embedding copyright information into digital media. The copyright information which is embedded in digital media is known as watermark. Watermarks are intended to be imperceptible to the end user of the digital media. Digital watermarking provides copyright protection, authentication, and content tracking information. Due to these widespread advantages, digital watermarking is utilized in a gamut of applications, such as image and audio protection, and video piracy preservation.
In audio/video watermarking, watermark is embedded in an audio/video media, in order to protect the media from illegal copying and to identify manipulations. The watermark is embedded using an algorithm and is perceptible to watermark-reading software only. Digitally watermarked media generally undergoes some modification after the time it is embedded. The modifications may be due to alterations done to the media or due to illegal distribution, copyright violation, etc. of the media. These modifications are commonly called as “attacks” and they degrade the quality of the watermark embedded in the media and render watermark's detection more difficult. Attacks are generally classified into unintentional and intentional attacks, wherein the intentional attacks are made during attempts to misuse or illegally distribute the media, undertaken by pirates. Intentional attacks generally have the objective to render the detection of watermark difficult. Unintentional attacks can be scaling, cropping, compressing, etc., of the digital media without any malicious intent of the doer. The common attacks of video watermarking are frame dropping, frame averaging, lossy compression, cropping, and various signal processing and geometrical attacks. It is desirable that watermark always remain in digital media, even if the digital media is subjected to such varied and different attacks.